Some people just forget Siri is there. Siri is something new and new things don’t always enter into, or find a place in, established workflows.

Siri not working — either because it doesn’t understand certain accents, because the required network connection fails, or because it simply takes too long to respond — causes enough frustration that some users simply abandon it and don’t go back. How many people would use Google if searches routinely took 30 seconds or more to return?

The inconsistent implementation — ability to read texts but not emails, ability to launch some apps for specific functions but not simply launch an app, etc. — creates an unpredictable or incomplete enough usability model that many simply exclude it entirely.

The lack of timely and consistent updates from Apple — only one new language in 6 months and no new features or integration — creates a wait and see attitude that, so far, is still waiting but not seeing.

The amount and type of Siri advertising creates expectations that the actual service (point #2) and support to date (point #4) don’t live up to, leading to dissatisfaction.